1. Field of the Invention
The present invention relates to automatic slack adjusters for selectively engageable friction couplings, such as cam actuated brakes, and in particular relates to improved automatic slack adjusters of the type comprising a lever housing in which a worm and worm gear are rotatably received and defining a bore opening to the exterior of the housing at a sleeve like projection which is formed integrally with the housing, the bore receiving a drive mechanism for controllably rotating the worm and worm gear which includes a piston axially slidable in the bore and extending partially therefrom. In the preferred embodiment, the piston is hollow and the internal lubrication system of the adjuster is configured so that presence of lubricant at or adjacent the exterior end of the bore is an indication of proper lubrication of the interior components of the adjuster. The improvement comprises sealing the exterior of the bore and/or the hollow end of the piston by means of a static seal, such as a resilient elastomeric boot, one end of which is sealingly received around the exterior of the sleeve like projection and providing a smooth continuous surface around the exterior of the projection in which a smooth continuous annular groove is formed.
2. Description of the Prior Art
Automatic slack adjusters for cam actuated brakes comprising a lever housing in which a worm and a worm gear are rotationally received and further comprising a drive mechanism for controllably rotating the worm and worm gear are known in the prior art. In particular, automatic slack adjusters having a housing defining a bore opening to the exterior of the housing at a sleeve like projection in which an axially slidable piston comprising a portion of the drive mechanism is received, a portion of the piston extending beyond the end of the bore, are known in the prior and may be appreciated in greater detail by reference to U.S. Pat. No. 3,507,369. It is known that continued satisfactory operation of such slack adjusters depends upon adequate lubrication of the internal mechanisms and proper sealing of the housing. The prior art mechanisms were not totally satisfactory as it was difficult to determine when the internal mechanism of the adjusters were adequately lubricated and/or to satisfactorily seal the exterior opening of the bore.